And so on for a number of countries. Arranged by country code and by year.

I found an example in the archives of how to calculate the growth
rates (http://www.stata.com/statalist/archive/2006-05/msg00529.html)
and yet when I try to do the same I get an error message 'Type
mismatch', no matter which variable type I enter. I typed the
following into the command box and came out with the output shown.